164 



APPLIED BIOLOGY 



of a branch ; this is a flower-scar. On a much larger twig, observe 

 the arrangement of the branches how does it compare with the 

 arrangement of the buds already noted? This is what we should 

 expect if the branches are merely developed 

 buds, as stated in the definition of a bud in the 

 next section. 



Make a sketch of the twig which has been 

 studied, showing as many of above points of 

 structure as possible. Compare with as many 

 twigs as possible lilac, apple, cherry, tulip- 

 tree, butternut, beech, and others named above 

 as possible substitutes for the horse-chestnut 

 branches. 



157. Buds. A bud is a growing point 

 on a plant which when conditions are favor- 

 able will develop into a leafy branch, a 

 flower, or both. In temperate regions where 

 plants must withstand a long cold winter, 

 trees and shrubs have formed the habit 

 of covering and protecting their growing 

 points with scales, hair, or gummy sub- 

 stances. The horse-chestnut bud is a good example of a scaly 

 or winter bud, and similar ones can be seen on any of our hardy 

 shrubs or trees. In annuals and herbaceous perennials of tem- 

 perate climates and in tropical countries where the growing 

 season is not interrupted by a winter season, with its sudden 

 changes of temperature and moisture, the buds as a rule have 

 either very little covering of scales or hairs, or none at all 

 (naked buds). 



Buds of Horse-chestnut. (L) Or hickory, lilac, elm, or any large 

 bud. Examine horse-chestnut buds and note that they are all 

 covered with sticky brown scales which overlap as do the shingles 

 on a house. Examine a bud cut longitudinally. Suggest a use for 

 the sticky substance. Carefully remove the scales from a bud and 

 observe the ring of scars left on the stem. This marks the end of 

 the year's growth of the stem. Look along the stem for other 

 similar rings of scars how many do you find ? What relation do 

 the number of such rings of scars bear to the age of the twig ? 



FIG. 43. Left twig, 

 horse-chestnut ; 

 right one, hickory. 

 (From Gray.) 



